Hi there, @MMLatJML.

As of now, the option to add the "Project Name" field on estimates and invoices is still unavailable. However, you can create Custom fields for each projects as a workaround.

Here's how:

1. Click the Gear icon at the upper right side.
2. Then, under the Lists tab, click the Customs fields.
3. Then, click the Add field button and fill out the name option.
4. Then, select the boxes where you would like to apply it.
5. Lastly, hit Save.

I suggest providing feedback to our software engineers so they can consider it for future updates.

Here's how:

1. Go to the Gear icon, then click Feedback.
2. Fill out your recommendation.
3. Hit Next to submit.

Suppose you have plans on creating purchase orders and send them to vendors. Here's the topic you can utilize for reference: Create and send purchase orders in QuickBooks Online

Please feel free to reach out if you've got more queries or need clarification. I'm just one post away.